1. Field of the Invention
The present invention relates to a water level controller, and more particularly to a water level controller with conductance terminals to control the water level in a tank.
2. Description of Related Art
Large amounts of water are used in many industrial processes. To accommodate the large quantities of water that are periodically required, tanks are used to store the reserve water. To keep the tank from running dry, a water level controller is mounted in the tank to control the water level in the tank. A conventional water level controller is a buoyant, hollow ball attached to one end a lever. The other end of the lever is pivotally connected to an inlet valve in the tank, such that the ball will move up or down according to the height of the water level as the ball floats on the surface of the water. When the water level goes down, the controller will open the inlet valve and allow water to flow into the tank to raise the water level in the tank. When the water level reaches some predetermined upper level, the controller will close the inlet valve and stop the water flowing into the tank. Thus, a water level controller is achieved.
However, because the tank for an industrial process is very huge, and the travel of the lever device is limited, the conventional ball controller with a lever device does not fit with a huge tank. Therefore, an another ball controller with a wire connected to the ball provided is used, such that the water level can be controlled based on the length of the wire. However, because the wire is flexible, the length of the wire may not be correct due to bends in the wire or the lateral movement of the ball relative to the water level.
In addition, a controller with a magnetic switch mounted on the ball is provided. Several magnetic sensors are mounted on the inner surface of the tank at different heights. When the ball falls with the water level and the magnetic switch faces the lowest magnetic sensor, the inlet valve will be opened to allow water to flow into the tank. When the magnetic switch is adjacent to the uppermost magnetic sensor, the controller will close the inlet valve and stop the water from flowing into the tank. Although the water level can be accurately controlled by the controller with a magnetic device, the controller does not operate properly when the ball moves laterally relative to the water level and the magnetic switch does not face the magnetic sensors. Therefore, the water level control by the ball controller is not accurate.
Another conventional controller comprises a light mounted on the top of the tank and a light meter mounted on the bottom of the tank to measure the intensity of the light through the water. The water level can be determined by the change in the intensity of the light measured by the light meter. The controller with the light meter can accurately control the water level. However, the light meter is not only very expensive, but is also able to receive light from any source. The light meter is easily influenced by other lights.
Another conventional controller with electrical terminals can detect the water level by sensing whether a desired electrical terminal is electrically connected with the other desired one through the ions in water or not. However, because pure, untreated water is often used in industrial processes, the water is so pure that it will not conduct electricity. Therefore, the conventional controller with electric terminals cannot used with pure water. The scope of using this conventional controller is limited.
To overcome the shortcomings, the present invention tends to provide an improved water level controller with conductance terminals to mitigate or obviate the aforementioned problems.
The main objective of the invention is to provide an improved a water level controller with control circuitry and multiple conductance terminals connected to the control circuitry and located at different heights such that the water level can be determined through the conductance of the water measured by the corresponding conductance terminals. Consequently, the water level in the tank can be accurately controlled, and the controller can be used with pure water.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.